Some industrial processes require handling of large cylindrical workpieces. For example, lumber mills must handle logs and position them for being cut by a saw. Positioning the log for cutting involves moving the log towards the saw and rotating the log into an optimal rotational orientation. The optimal rotational orientation of a log for cutting is that orientation that will obtain the highest yields of the most desired cuts of lumber. To find the optimal rotation orientation, a laser scanner scans the surface of the log and generates scan data. A processor then takes the scan data and constructs a three dimensional model of the log. The same processor or a different processor can then run an algorithm on the three dimensional model of the log to determine a set of optimal cuts to make and the optimal orientation for the log to be in for the saw to make the set of optimal cuts. The optimal cuts and optimal orientation may not be the ultimately best solution, but may be the best found by the algorithm according to a set of process criteria.
Boyd (U.S. Pat. No. 7,857,021) describes one such system and method for positioning a workpiece in an optimized position. A marking device places a mark on the workpiece prior to the workpiece passing through a scanner. Boyd teaches a spray paint line placed on an end of the workpiece, making a superficial cut or identifying a natural feature of the workpiece. The mark is used as a point of reference while rotating the workpiece relative to the orientation of the mark. The workpiece is then scanned. Using the resulting scanning data, an optimizer processor determines the optimal rotational orientation of the workpiece for processing. An initial orientation of the workpiece is identified by a first camera. A turning mechanism rotates the workpiece to the optimal rotational orientation. A second camera identifies the orientation of the mark while the workpiece is being rotated. A processor compares in real time the orientation of the workpiece with the optimized position to determine if the workpiece is in the optimized position.
This system and method of Boyd has several flaws. The first flaw is that it requires a mark to be placed on the workpiece. The mark will remain on some of the pieces of the workpiece after it is cut. In most cases, this mark is undesirable on the finished pieces and removing it will be impractical or at least an added expense. The second flaw of the method of Boyd is insufficient accuracy. Depending on the method of making the mark, the mark may not have very sharply defined edges. This will impair the accuracy of tracking the rotational orientation of the workpiece. A third flaw of the method of Boyd is that the time it takes to perform the optimization algorithm. If a detailed optimization is performed, it may delay the processing of the workpiece, decreasing the productivity of the lumber mill. A crude optimization would be quicker and avoid delay, but better optimization solutions may be missed, resulting in needless waste and loss of value in the product cut from the workpiece.
What is needed is a method for more accurately optimizing the rotational orientation of a workpiece without marking the workpiece and minimizing delay in calculating the optimized orientation.